Servo brake



Sept. 19, 1929.'

F. ATHIMON S ERVO-BRAK E 4 Sheets-Sheet 1 Filed Sept. 50, 1927 v sept. 1o, 1929. RM1-,MON 1,727,742

SERVO-BRAKE Filed Sept. 50, 1927 4 Sheets-Sheet 2 Sept. 10, 1929.

F. ATHIMON SERVO-BRAKE Filed Sept. 30, 1927 4 Sheets-Sheet 5 sept. 1G, 1929. E ATHIMO'N 1,727,742

' SERVO-BRAKE Filed Sept. 50, 1927 4 SheetS-Sheet 4 Patented Sept. 10, 1929.

UNITED STATES FRANCIS ATHIMON, 01E' PARIS, FRANCE.

SERV() BRAKE.

Application filed September 30, 1927, Serial No. 223,168, and in France October 6, 1928.

ln braking devices, when the pedal is operated, after having taken up the inoperative stroke, a much greater resistance appears, which increases with the braking action.

During said latter stroke all the control members (from the pedal to the drums) are subjeeted to an elastic deformation proportional to the pressure exerted. When the brakes are released, these control members assume again their `natural state and are able to yield an energy which heretofore was not utilized.

The device of the present invention permits recovery of this energy which is then emr ployed for the braking and to obtain also a maximum braking action Without a great effort from the driver.

In the braking device according to the present invention, a spring preliminarily compressed at a tension equal to the major part of the tension required for setting on the brakes and for causing the elastic deformation of all the control members cooperates with the drivers effort during the braking action and is brought back to its initial state by the elastic tension of the control members when these latter are released. The invention has further for its object to combine such mechanism with a suitable device for taking up the Wear whereby the inoperative stroke will be made constant, i. e. the braking may be commenced in all cases after a given initial displacement of the brake pedal or lever, irrespeetivcly of the Wear of the brakes, or otherwise stated, the mechanism Will be constantly brought to the inoperative position by the elastic reaction of the rod-and-link gear, and the action of the relay spring Will never be preponderant.

The appended drawings show by way of example various embodiments of the invention.

Fig. 1 is a cross-section of the apparatus on the line 1-1 of Fig. 3, showing the first form of construction, and

Fig. 2 is a corresponding view in the maximum braking position.

Fig. 3 is a plan view of the apparatus, with the cover and the spring removed.

Fig. 4 shows the pawl in the raised position,

the section being taken on the line 4 4 of Fig. 1.

Fig. 5 is a diagram relating to the automatic connection between the d1splacement of the main lever and the movement of the rollers, and

Fig. 6 is a modification.

Fig. 7 is a vertical section on the line 7-77 of Fig. 9 relative to a construction embodying the principles shown in Fig. 6.

Fig. 8 is a vertical cross-section on the line 8--8 of Fig. 7.

Fig. 9 is a plan view of the apparatus with the cover removed.

Fig. 1() is a horizontal section on the line 10-1O of Fig. 8.

The apparatus forms a compact device which is preferably secured by means of its casing 1 to the cross-piece of the vehicle frame. The rod 2 is connected With a pedal, 70 not shown, which is loose on its axle, and the rod 3 is connected with the lever 4 by which all the brakes are operated (not shown) Upon the casing or frame 1 (Fig. 1) is disposed the lever 4 which is pivotally mounted 75 on the tivo overhung axles 5; said lever has preferably a U section. Between and along the lateral fianges of the U piece are adapted to roll two coaxial rollers, ball-bearing members, or the like, 6; the latter are mounted on 80 the axle 7 on the respective sides of'a link 8 which is inserted through a. slot formed in the lever 4. The other end of the link 8 has the shape of a fork and is pivotcd to an axle 9 mounted on a sliding member 10 Which-l-by 85 means of the concave piece 11 and the nut 12-is urged by the preliminar-ily compressed spring 13. On the upper end of the lever 4 is mounted the axle 14 through the middle part of which passes the rod 3. A ratchet nut 90 15 is screwed on the threaded end of the rod 3 and bears on the axle 14. 0n one end of said axle 14 is pivotally mounted the small lever 16 whereof one end is connected with the rod 2 and the other end is slotted in order'to limit 95 the motion of the lever 16 with respect to the lever 4 by coacting with the stud 17 on the lever 4. The said stud also serves as a stop for the rollers 6, and it holds their axle 7 in the position shown in Fig. 1) exactly in line 100 l with the axles 5, when the apparatus is in the inoperative position.

The upper part of the casing 1 is closed by a tight cover 34.

In the following description, for the sake of simplicity, the lever 16 may be considered as secured to the lever 4, and the lever 4 may be considered as a relay device in the general control of the brakes.

Vhcn the apparatus is in the inoperative position the stud 17 bears on the left'side of the slotted end of the lever 16 and the rollers 6, which are subjected to the action of the spring 13, exert on the lever 4 a pressure in a direction passing through the centre of the axles 5 (the rollers being concentric with said axles), and have nocifect as to the rotation of the lever 4. Vhen the brake pedal is pressed down, the rod 2 is moved in the direction ot the arrow f; this actuates the lever 4 and all parts pertaining thereto, thus bringing it from the inoperative position to the intermediate position illustrated i-n Figure 1 (beginning of the braking action). During this period, the axle 7 of the rollers 6 remains stationary. As the movement continues, the roller path inclines under the rollers 6 which will gradually7 be moved downwards, by roason of the outline of the said roller path, and at the end of the braking action they will attain a position corresponding to the position illustrated in Figure 2.

n this position, due to the great lever arm .the action of the spring 13 on the lever 4 will .be a maximum, as well as upon the brakes,

through the rod 3. In this position, al though the spring 13 is somewhat expanded, it is by no means in the fully expanded position; herein its expansion may be for instance 5 mm. whilst the maximum expansion is 40 mm. If forexample it is neces-l sary to exert a traction of 400 kgs. upon the rod 3 to obtain the maximum pressure of the brakes, 350 kgs. may b e balanced by the action of the spring 13, leaving 50 kgsto be applied by the driver on the rod 2. Upon releasing the pedal, the elastic tension of the brakes becomes preponderant and will bring the spring 13 to its starting tension, so that the rollers 6 and the lever 4 will be brought back to the position shown in Figure 1 and then to the inoperative position. Since the traction on the rod 3 increases with the comling down of the rollers and consequently spring 13 might become excessive, and for this reason I employ automatic means for taking up the wear which will be further described.

Adjacent the ratchet nut 15 is pivoted a pawl 18 upon the lever 4, by means of the screw 19; said pawl is controlled by the spring 18b and it carries an arm in the form of a. circular arc 18a which is concentric with the pivotal axis 5 of the lever and which is cut on a bevel (Figure 4). Irrespectively of its angular position, the arm 1821 is subjected to the action of the notched edge of a lever 20 which' is pivoted to an axle 22 secured to the stationary part 21 of the casing 1; said lever 2O is terminated by a branch 2()n situated adjacent a screwthreaded rod 23 adjustably screwed in an arm 16l of the small lever 16. A spring 24 is connected at one vend with said arm 16a and at the other end with the lever 4 by means of the nib 25. This spring 24 urges the arm 16a towards the nib 25 and causes the left side (Figure 1) of the slotted end of the lever 16 to bear on the' stud 17. The tension of said spring 24 is sufficient for not yielding during the movement from the inoperative position to the position shown in Figure 1, that is to say that during saidrinoperative stroke, the lever 4, the spring 24 and the lever 16 are bodily pivoted as a whole about the axles 5. The lever 16 begins only to rotatev about the axle 14 substantially beyond the position shown in Figure 1, that is at thc beginning of the proper braking action. At this moment, the lever 16 rotates about the axle 14 and drives with it thevarm 16 and the rod 23 until the stud 17 bears on the right side (Figure 1) of the slotted end of the lever 16. rlhe rod 2 is then moved bodily with the lever 16, the axle 14 and the lever 4 about the axles 5, when said rod 2 is further moved to the right. As will be observed'by comparing Figs. 1 and 2, the pawl 18 is movable. on the ratchet nut 15 by the displacement of the lever 4; when returning, it tends to engage one of the ratchet teeth and thus to tighten the brake control. The form of the ratchet teeth is such that the pawl will be about to leave the tooth with which it is engaged, when the lever 16 is in the position shown in Figure 1. Then the rod-and-link gear is properly adjusted, it is necessary that the pawl 18 be prevented to engage the following tooth of the nut 15. For this purpose, when the braking action begins in the position shown in Figure 1, the lever 16 rotates about the axle 14 with the arm 16a and the rod 23; this latter presses against the projection 20b on the branch 26n of the lever 20 and causes said lever 20 to turn about the axle 22. As shown in Figure 4, during the downward movement of the upper branch of the lever 20, said upper branch by means of a ramp 50 thereon presses on the bevel part of the arm 18L and holds it in a locking notch 51 of the lever 20: the pawl 18 is thus disengaged from the ratchet nut and is held in said position during the entire braking as far as the inoperative position; at a short Idistance before reaching said latter position, a sto member 26, carried on the lever 4 and rotating with said lever 4 about the axles 5 from the position shown in Figure 1 to the inoperative position, raises the upper branch of the lever 20 and disengages the pawl 18 which falls in the same tooth of the ratchet nut 15. If the rod-and-link gear is not properly adjusted, the braking action will onl y begin beyond the position shown in Figure 1 and the rod 2 will rotate further about the axles 5, the lever 4, the lever 16 and the rod 23. The rod 23 will thus slide on a portion of the projection\20b without displacing said projection.

-When the braking action begins, the lever 16 and the rod 23 are rotated about the axle 14. The rod 23 slides on the remaining por tion of the projection 20" and rotates the lever 20; but said remaining portion of the lprojection 20" being4 insulicient, the rod 23 `:tails from said projection before the upper branch of the lever 20 has been lowered sufficiently for causing the locking notch 51 of the lever 20 to engage the bevel of the arm 18a. The pawl 18 falls thus again on the ratchet nut, rotates with the lever 4, engages the following tooth ot the ratchetnut and, during the return stroke of the brakes to the inoperative position, screws the ratchet nut for one tooth, thus taking up the excessive play which is occasioned by the wear or otherwise.

Due to the action of these parts, the starting ofthe braking action is maintained at the same point irrespectively of the wear of the brakes.

The diagrammatic view Fig. 5 shows the relation between the angular displacement of the lever 4 and the descent of the rollers 6 upon said lever during the braking. a', b', e represent three successive positions of the pivoting pin connecting the control rod 2 to the lever 16. To these three positions correspond the three positions a, Z), c of the rollers 6. The point e corresponds to the inoperative position of the axle 19 and moves to the lett during the braking action. The curve Z represents the displacement of the rollers 6 eoncentrically about e. The roller path ol the lever 4 has been chosen with a radius substantially greater than that of the curve d. At the beginning of the proper braking action, said roller path is represented b v the line c and has its center on :c: it will be seen that the traction exerted by the spring 13 is in this position perpendicular to 'the curve a.

lVhcn the pivoting pin between rod 2 and lever 16 is in the position b, the lever 4 has been rotated about pivot 5 so that the roller 3 leading to the brake.

path will assume the positionb and that the center of said roller path will come on y: the traction of the spring 13 will still be made perpendicularly to the curve b. The same will be true when the rollers 6 will be in 0 on the roller path which will then assume the position c with the center e. VIt will thus be seen that the bearing point of the arm or link 8 on the pivoting lever 4 is always in equilibrium for any braking position.

Fig. 6 shows by Way of example a modiiied arrangement whereby the relay spring is placed in action; herein the lever 27 is substituted for the lever 4. The automatic regulating parts remain the same as before, as also the control rods 2 and 3.- The end of the lever 27 has an outline which is concentric with the axis 28.l A round end at 29'is in contact with a roller 30 mounted on the lever 31 which is pivoted at 32 and is suitably maintained by the traction of a spring 33. From the position `D to E, which dis placement corresponds to the inoperative stroke, the lever 27 is unaffected by the spring 33, the roller 30 being in contact with the concentric part. From the position E to F, the lever 27 is drawn by the spring 33 with a force which increases with its displacement, this being practically proportional for a small angle such as is represented in the position F. The tension of the spring 33 is applied on the lever 27 by the tangential surfaces 29 and 30; the direction of the effort is thus perpendicular to the point of contact of said surfaces. On account of the shape of the curve 29, said direction varies and starts from a line passing through the pivotal axis 28 and becomes more and more distant from said axis: the lever arm of the effort causing the rotation of the lever'27 becomes thus greater and greater.

Figs. 7 to 10 show a form of construction' of the device represented diagrammatically-in Fig. 6. The apparatus is placed between the rod 2 leading to the brake pedal and the rod To the rod 2- is secured the lever 16 pivoted at 14 to the lever 27, which is pivotally mounted on the axle 28. The lever 27 comprises at the ,lower part a cylindrical portion a b which is concentric with the axis 28, and an eccentric ramp 29 extending from b to o. By means of said cylindrical portion and said ramp, the lever 27 bears upon the roller 30 which is mounted by ball-bearings on the shaft 34 carried by two parallel levers 31 pivoted on the axle 32 which is mounted in two respective holes in two plates 35 secured to the casing; said plates are pierced with various holes 36 having the same diameter as the axle 32 and whose centres are situated on an areof a circle having the axis 34 as a centre. Upon the axle 34 are mounted on the respective sides of the roller 30 two rollers 37 of a somewhat larger diameter; said rollers make contact with a lever 38 which comprises two vertical lugs 39-40 and is pivoted-on an axle 41 secured to the casing. By means ot the screw 42, the slide 43 is movable between the lugs 39 and 40, and it makes contact with the plate spring 33 secured to the casing at 4l.

The operation is as follows:

By the action ot' the spring 33, the lever 38 is subjected to a couple C1 whose magnitude can be changed, by means ot the slide 43, by the displacement ot the point of application of the force. Variable eil'orts may thus be applied on the lever 27 for a same expansion of the spring 33. The lever 38 acts upon the rollers 37 which are subjected to a couple C2 by which the rollers andthe levers 3l are pivoted on the axis 32 and to a tangential force by which the rollers 37 are rotated on their axis. The couple C2 is lnanii'ested by a force l" perpendicular to the surface of' contact between the roller 3() and the lever 27; said force produces a couple rotating the lever 27 when it does not pass through the axis 28.

In all positions of the lever 2T between the inoperative position (on the right of the position shown in Figure 7) and the position shown in Figure 1, the point of application of the force is situated between (L and l). This force passes through the axis 28 and has no effect on the rod 3; but when the lever 27 is further moved to the left (Figure 7) the direction of the force passes through the contres of curvature of the curve bc which differ from the axis 28, so that the lever 27 is subjected to a couple Whose moment increases from zero to a maximum value which is attained at the end of the stroke. In this position, the spring 33 is somewhat expanded, but is far from its maximum expansion. For the maximum braking, if 'I kgs. traction are required for the maximum brake pressure, (rf-t) kgs. will be balanced by the action o the spring, and there will remain t kgs. to be furnished by the driver. Since the traction of the rod 3 increases with the displacement of the lever 27 to the lett, and since the action of the spring is proportional to this displacement, the same proportion between the aid furnished by the spring and the effort to be exerted by the driver will be maintained throughout the entire braking stroke. When the driver ceases his effort, the elastic tension ot the brakes will preponderate and will give the spring the tension which it had at the'start. v

According to the position of the axis 32, I may advance or delay the time at which the roller 37 is brought into contact with the point c of the curve b c corresponding to the maximum braking. It will thus be possible to vary the stroke of the rod 2 and consequently of the pedal or operating lever for obtaining the' maximum braking.

The apparatus herein described can be completed to advantage by the device for taking up the wear as above specified. Said device chiefly comprises a ratchet nut 15 which is mounted on the end of the rod 3, and a pawl 18 which is secured by the screw 19 to the lever 27; said pawl is provided with a reaction spring 18b and it comprises an arm 18a of circular arc shape which makes contact with the end of a lever 20, pivotally mounted at 22. The lever 2O is actuated at 20a by a rod 23 secured to the lever 16.

l Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a brake control mechanism the combination of a control member adapted to be moved by an operator, reacting means adapted to be moved and to be elastically deformed by said control member, a tensioned spring and means adapted to transmit the tension oi." said spring to said reacting means when the control member is operated, whereby said reacting means are further elastically deformed, and to bring back said spring to its initial state by the elastic tension of the reacting means when the control member is released.

2. In a brake conrol mechanism the combination ot' a control member adapted to be moved by an operator, reacting means adapted to be moved and to be elastically deformed by said control member, a tcnsioned spring and means adapted to transmit gradually the tension of said spring to said reacting means when the control member is operated, Whereby said reacting means are further elastically deformed, and to bring back said spring to its initial state by the elastic tension of the reacting means when the control member is released.

3. In a brake control mechanism, the combination of a control member adapted to be .move-d by an operator, reacting means adapted to be moved and to be elastically deformed by said control member, a connecting member pivoted to said control member, to said react ing means and to a stationary pivot, a tensioned spring, and means adapted to transmit the tension of sai-d spring to said connecting member along variable directions differently distant from said stationary pivot when the control member is operated, whereby said reacting means are further elastically deformed, said spring tension transmitting means being also adapted to bring back said spring to its initial state by the elastic tension of the reacting means when the control member is released.

4. In a brake control mechanism, the combination of a control member adapted to be moved by an operator, reacting means adapted to be moved and to be elastically deformed by said control member, a connecting member pivoted to said control member, to said reacting member and to a stationary pivot, a rocking arm adapted to exert on said connecting member a pressure along directions at diii'erent distances from said stationary pivot and a spring adapted to urge said rocking arm against said connecting member.

5. In a brake control mechanism, the combination of a control member adapted to be moved by an operator, reacting means adaptA ed to be moved and to be elastically deformed by said control member, a connecting member pivoted to said control member, to said reacting member and to a stationary pivot, a rocking arm provided with a roller bearing on said connecting member and adapted to exert on said connecting member a pressure along directions at diilerentdistances from said stationary pivot and a spring adapted to urge said rocking arm against said connecting member.

(i.4 In a brake control mechanism, the combination of a control member adapted to be moved by an operator, reacting means adapted to be moved and to be elastically deformed by said control member, a connecting member pivoted to said control member, to said reacting member and to a stationary pivot, a rocking arm adapted to exert on said connecting member a pressure in a direction in line with said stationary pivot and in directions differently distant from said stationary pivot and a spring adapted to urge said rocking arm against said connecting member.

7. In a brake control mechanism, the combination of a control member adapted to be moved by an operator, reacting means adapte ed to bemoved and to be elastically deformed by said control member, a connecting member pivoted to said control member, to said reacting member and to a stationary pivot, a cam surfaceon said connecting member, a tensioned spring, a rocking arm adapted to bear on said cam surface and to transmit thc tension of the spring on said cam surface along variable directions differently distant from said stationary pivot when the control member is operated.

S. In a brake control mechanism, the combination of a control member adapted to be moved by an operator, reacting means adapted to be moved and to be elastically deformed by said control member, a connecting member pivoted to said control member, to said reacting member and to a stationary pivot, a cam surface on said connecting member, a tensioned spring, a rocking arm adapted to bear on said cam surface and to transmit the tension of the spring on said cam surface along variable directions diii'erently distant from said stationary pivot When the control member is operated, said cam surface comprising a part Where said rockmg arm bears m a stable equilibrium upon said cam surface for a limited angular movement of said connecting member.

9. In a brake control mechanism, the combination of a control member adapted to be moved by an operator, reacting means adapted to be moved and to be elastically deforme-d by said control member, a connecting member pivoted to said control member, to said reacting member and to a stationary pivot, a lam surface on said connecting member, a tensioned spring, a rocking arm adapted to bear on said cam surface and to transmit the tension of the spring on said cam surface along variable directions differently distant from said stationary pivot when the control member is operated, said cam surface coinprising a part having a radius substantially greater-than the length of said rocking arm in order that the bearing point of the rocking arm on said connecting member be always in equilibrium.

l0. In a brake control mechanism the combination of a control member adapted to' be moved by an operator, reacting means adapted to be moved and to be elastically deformed by said control member, a tensioned spring, means adapted to transmit the tension of said spring to said reacting means when the control member is operated, whereby said reacting means are further elastically deformed, and to bring back said spring to its initial state by the elastic tension of the reacting means when the control member is released and an automatic device adapted to maintain the same elastic tension in said reacting means for a same position of said control member.

1l. In a brake control mechanism, the combination of a control member adapted to be moved by an operator, reacting means adapted to be moved and to be elastically deformed by said control member, a connecting member pivoted to said control member, to said reacting means and to a stationary pivot, a tensioned spring, means adapted to transmit the tension of said spring to said connecting member along variable directions differently distant from said stationary pivot when the control member is operated, whereby said reacting means are further elastically deformed, said spring tension transmitting means being also adapted to bring back said spring to its initial state by the elastic tension of the reacting means when the control member is released and an automatic device carried by said connecting member and adapted to maintain the same elastic tension in said reacting means for a same position of said control member.

12. In a brake control mechanism, the combination of a control member adapted to be moved by an operator, a reacting member adapted to be moved and to be elastically deformed by said control member, a connecting member' pivoted to said reacting member and to a stationary pivot, a spring controlled lostmotion device interposed between said con trol member and said connecting member, a tcnsioned spring adapted to eXert a pressure ou said connecting member along variable directions differently distant from said stationary pivot when said control member is moved, a slack adjuster associated with said reacting member', means controlled by said connecting member for actuating said slack adjuster during the return movement of the connecting member, and means controlled by said lost-motion device for making said slack adjuster actuating means inoperative When said lost-motion device'operat'es Within a limited initial angular movement of said connecting member.

13. In a brake control mechanism, the combination ot' a control member adapted to be moved by an operator, a reacting member adapted to be moved and to be elastically deformed by said control member, a connecting member pivoted to said reacting member and to a stationary pivot, a lever pivoted to said control member and to said connecting member at a point different from said stationary pivot, a spring attached on said connecting member and on said lever, a stop on said connecting member in the path ot said lever, a tensioned spring adapted to exert a pressure on said connecting member along variable directions diierently distant from said stationary pivot when said control member is moved, a slack adjuster associated with said reacting member, means controlled by said connecting member for actuating said slack adjuster during the return movement of the connecting member, and means controlled by said lever for making said slack adjuster aetuating means inoperative when said lever operates Within a limited initial angular movement of said connecting member.

14. In a brake control mechanism, the combination of a control member adapted to be moved by an operator, a reacting member adapted to be moved and to be elastically deformed by said control member, a connecting member pivoted to said reacting member and to a stationary pivot, a lever pivoted to said control member and to said connecting member at a point dilfcrent from said stationary pivot, a spring attached on said connecting member and on said lever, a stop on said connecting member in the path of said lever, a tensioned spring adapted to exert a pressure on said connecting member along variable directions dii'erently distant from said stationary pivot when said control member is moved, a ratchet nut screwed on said reacting member and adapted to bear on said connecting member, a. pawl pivoted to said connecting member and adapted to bear yieldingly on said ratchet nut, the circumferential length of the teeth of said ratchet nut being substantially equal to the distance through which said pawl is displaced during a limited initial angular movement of said connecting member, a circular member concentric with said stationary pivot secured on said pawl, a movable push-piece adapted to bear on said circular member and to bring said paWl away from said ratchet nut, a limited projecting surface provided on said movable push-piece and a contacting member operatively connected with said lever and adapted to slide on said projecting surface without moving said push-piece when said lever rotates about said stationary pivot and to slide on said projecting lsurface While moving said push-piece when said lever is rotated on said connecting member.

In testimony whereof I have signed my name to this specification. i

FRANCIS ATHIMON.

llU 

